I mean that it would be awesome, what else? Replace the 10 boring Gnome and KDE games with something genuinely captivating and start eroding the "Linux doesn't have games" mindset.
If you are thinking that this won't have any effect in the long run, allow me to politely disagree. In my country, every 11-year-old child recently acquired a free netbook with Ubuntu pre-installed (on most of them at least). Pretty much each one of those lads (and ladies) I have spoken with likes Ubuntu more than their WinXP installations - and pretty much all of them run WinXP anyway, because "games don't work on Ubuntu".
Some of them have discovered the Ubuntu Software Center and started installing games from there (I was mightily surprised when I saw my cousin playing bzflag on an impromptu lan party!) but that's still not enough: no Starcraft, no Counterstrike, no Unreal Tournament (all of those run but are far too slow to be playable on Wine - plus, Wine is far too difficult to setup).
My point? Add a few quality games to Ubuntu and people *will* come. That's all.
The games in Ubuntu's standard installation are there because they're free as beer, and I guess a Solitaire or Sudoku doesn't take much space on the CD.
I doubt games in the Humble Indie Bundle qualify.
Now if you mean having them in the standard repositories available out-of-the-box through the software center (if I remember correctly Mark Shuttleworth mentioned offering proprietary apps there too in the longer run), then yes sure.
Now Steam is on its way too, though I don't know about their licensing model requirements. If it's any indication, World of Goo is already available from the MacOS port, and it's the only game from the bundle that won't offer the source code...
There are enough really cool foss games around, don't know why they aren't installed by default. Perhaps some of them don't work on all machines (3d acceleration, etc), but at least Frozen Bubble works everywhere, and is awesome.
I must admit that was a lie. I compared it to the Windows version now and while the Linux version is playable, scrolling is so much smoother under Windows. I didn't realize the slight stuttering first, but now that I know how it has to perform, I would love to see some performance tweaks too.